Five steering committees examine the literature


Clinical Pulmonary Medicine
Asthma-COPD overlap: An underappreciated phenotype of obstructive airway disease (OAD)

Asthma-COPD overlap (ACO) is a common yet underappreciated clinical entity within the complex OAD spectrum. Currently, there is no consensus criteria to define ACO; however, a roundtable consensus from an international group (Sin et al. Eur Respir J. 2016 Sep;48:664) suggests using major and minor criteria, with key features being airflow limitation, asthma history, and cigarette or biomass exposure. Several studies have shown that patients with ACO have severe disease, faster lung function decline, greater morbidity and mortality, and lower QoL (Alshabanat et al. PLoS One. 2015 Sep 3;10:e0136065).

Dr. Munish Luthra

Dr Munish Luthra

There is paucity of data on the pathophysiology, risk factors, and clinical management given exclusion of these patients from clinical trials of asthma and COPD. Indeed, clinicians and researchers now realize that ACO is an umbrella term for multiple subphenotypes, including patients who have predominant asthma with some COPD features and others with predominant COPD with some asthma features. Overall, IgE level, FeNO, sputum, and blood eosinophils are usually higher in ACO than in COPD and relatively similar compared with asthma (Kobayashi et al. Int J Chron Obs Pulmon Dis. 2016 May 26;11:2117).

Dr. Samantha D'Annunzio

Dr. Samantha D'Annunzio

Most recently, a longitudinal study looked at predictors of ACO among NY firefighters exposed to WTC dust (Singh et al. CHEST. 2018 Dec;154[6]:1301). Pre-exposure low lung function and elevated blood eosinophils and IL4 (T2 inflammatory cytokine) increased risk of developing ACO among those exposed to WTC dust. Further research is required to better understand the interaction of environmental exposure and risk factors in the pathophysiology of ACO. It may be more pragmatic to use the unifying term OAD, as originally proposed in the Dutch hypothesis, and further delineate how several phenotypes of airway disease can be classified by combining traditional approaches with molecular and genomic analysis.

Munish Luthra, MD, FCCP
Steering Committee Member

Samantha D’Annunzio, MD
Steering Committee Member

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